Novellus Systems (NASDAQ: NVLS) announced today that it has developed precision anti-reflective layer (ARL) patterning films on its VECTOR PECVD platform with less than 2 angstroms wafer-to-wafer thickness variability.

The new process technology utilizes VECTOR's multi-station sequential processing (MSSP®) architecture to deposit ARL films with ultra-uniform film thickness, refractive index (n), and extinction coefficient (k). The properties of these new films exceed the requirements of sub-32nm lithography and are significantly superior to similar films deposited using a side-by-side single station-like deposition architecture.

Control of critical dimension (CD) variation is essential for 32nm lithography and beyond. The 2009 International Technology Roadmap for Semiconductors (ITRS) recommends less than 1nm total CD variation to ensure the functionality of ultra-high performance circuits. Advanced lithography CD control tools such as high-end phase-shift masks with complex optical proximity correction have become extremely expensive to implement in order to achieve the tight CD control required for 32nm device manufacturing. An effective, less expensive lithography technique used to control variability is called dose compensation, where the exposure dose is adjusted using a software algorithm for a specific area on the wafer. To ensure proper performance, dose compensation strategies require predictable anti-reflective layer thickness and optical properties for each incoming wafer. Novellus engineers have developed a new ARL process technology on the VECTOR platform that provides the ultra-uniform wafer-to-wafer performance required to employ these dose compensation control strategies. The new process technology is coupled with the VECTOR's angular placement accuracy of less than 0.3 mm to ensure the predictable film properties required for sub-32nm lithography. Figure 1 shows ARL film thickness profiles for wafers processed on a VECTOR with MSSP and those deposited using a side-by-side single station-like deposition. The film thickness maps for the VECTOR ARL films show low within-wafer and wafer-to-wafer variability, with a predictable profile for each wafer. In contrast, the ARL films deposited on the single station-like architecture have large wafer-to-wafer variation, which can compromise a dose compensation control strategy.

"The new generation of precision ARL films developed for the VECTOR platform have ultra-uniform thickness and optical properties that are essential for CD control at advanced technology nodes," said Kevin Jennings, senior vice president of Novellus' PECVD business unit. "As dual and triple-layer PECVD ARL films are employed for reflectivity control, VECTOR's inherent process control will enable the efficient use of feed-back and feed-forward CD control solutions."